JP2004277749A - Thermally peelable pressure-sensitive adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermally peelable pressure-sensitive adhesive sheet whereby an effective contact area is secured even when the bonding area of an adherend is small, preventing generation of adhesion troubles such as chip-scattering. <P>SOLUTION: The thermally peelable pressure-sensitive adhesive sheet comprises a thermally expandable pressure-sensitive adhesive layer containing thermally expandable microspheres, at least on either side of a substrate, and is characterized in that the thermally expandable pressure-sensitive adhesive layer has ≤0.4 μm average surface roughness at the central line before heating, and is allowed to have ≤5 μm maximum surface roughness before heating. The adhesive sheet may have a rubbery organic elastic layer between the substrate and the adhesive layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heat-peelable pressure-sensitive adhesive sheet that can be easily peeled from an adherend at any time by a short-time heat treatment.

  2. Description of the Related Art A heat-peelable pressure-sensitive adhesive sheet provided with a pressure-sensitive pressure-sensitive adhesive layer containing a foaming agent such as heat-expandable microspheres or a swelling agent on a base material has been conventionally known (Japanese Patent Publication No. 50-13878, Japanese Patent Publication No. Sho-51). JP-A-24534, JP-A-56-61468, JP-A-56-61469, JP-A-60-252681, and the like. This heat-peelable pressure-sensitive adhesive sheet is a pressure-sensitive adhesive sheet that has both adhesiveness and releasability after use, and has a reduced adhesive strength by foaming or expanding a foaming agent or the like by heating, and is easier than the adherend. It has the characteristic that it can be peeled off. Therefore, it is used as a temporary fixing means or a label for recycling in a manufacturing process of an electronic component.

  In recent years, electronic devices have become lighter, thinner, smaller, smaller and lighter, and with this, electronic components such as capacitors and LEDs to be mounted have also been made smaller and more chips. The above-mentioned heat-peelable pressure-sensitive adhesive sheet is also used for temporary fixing at the time of cutting these electronic components. However, as the size is reduced, the area to be bonded per chip is reduced. It is important to secure an effective contact area with the chip as a measure against troubles such as chip flying and chipping. However, in the conventional heat-peelable pressure-sensitive adhesive sheet, the unevenness due to relatively large particles among the thermally expandable microspheres added to the surface of the pressure-sensitive adhesive layer is not small. In some cases, an effective bonding area could not be secured, and chip flying and chipping might occur.

Japanese Patent Publication No. 50-13878 Japanese Patent Publication No. 51-24534 JP-A-56-61468 JP-A-56-61469 JP-A-60-252681

  Therefore, an object of the present invention is to provide a heat-peelable pressure-sensitive adhesive sheet which can secure an effective contact area and prevent the occurrence of bonding defects such as chip flying even when the area to be bonded of an adherend is small. Is to do.

  The present inventors have conducted intensive studies to achieve the above object, and as a result, when the center line average roughness of the surface of the heat-expandable pressure-sensitive adhesive layer before heating is set to a specific range, adhesion such as chip flying accompanying miniaturization of the chip becomes small. The inventors have found that defects can be suppressed and completed the present invention.

  That is, the present invention is a heat-peelable pressure-sensitive adhesive sheet provided with a heat-expandable pressure-sensitive adhesive layer containing heat-expandable microspheres on at least one side of a substrate, wherein the center line of the surface of the heat-expandable pressure-sensitive adhesive layer before heating is provided. Provided is a heat-peelable pressure-sensitive adhesive sheet having an average roughness of 0.4 μm or less.

  According to the heat-peelable pressure-sensitive adhesive sheet of the present invention, an effective contact area can be ensured even when the area to be adhered to an adherend such as a chip is small, and the occurrence of adhesion failure such as chip fly is prevented. be able to.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as necessary. FIG. 1 is a schematic sectional view showing an example of the heat-peelable pressure-sensitive adhesive sheet of the present invention, and FIG. 2 is a schematic cross-sectional view showing another example of the heat-peelable pressure-sensitive adhesive sheet of the present invention.

  In the example of FIG. 1, a heat-expandable pressure-sensitive adhesive layer 3 is provided on one surface of a substrate 1, and a separator 4 is laminated thereon. In the example of FIG. 2, a heat-expandable pressure-sensitive adhesive layer 3 is provided on one surface of a substrate 1 with a rubber-like organic elastic layer 2 interposed therebetween, and a separator 4 is further laminated thereon.

  The substrate 1 serves as a supporting base for the heat-expandable pressure-sensitive adhesive layer 3 and the like. Generally, a plastic film or sheet is used, but paper, cloth, nonwoven fabric, metal foil, or the like, or a laminate of these and plastic is used. An appropriate thin leaf such as a laminate of plastic films (or sheets) can be used. The thickness of the substrate 1 is generally 500 μm or less, preferably 1 to 300 μm, and more preferably about 5 to 250 μm, but is not limited thereto. The surface of the substrate 1 is formed by a conventional surface treatment such as chromic acid treatment, ozone exposure, flame exposure, high piezoelectric shock exposure, ionizing radiation treatment or the like in order to enhance the adhesion with the heat-expandable adhesive layer 3 or the like. Alternatively, oxidation treatment or the like by a physical method may be performed, and in order to impart releasability from the heat-expandable pressure-sensitive adhesive layer 3 or the like, for example, coating with a release agent such as a silicone-based resin or a fluorine-based resin is performed. Processing may be performed.

  The substrate 1 includes a low-adhesion substrate and a strongly-adhesive substrate. Examples of the low-adhesion base material include a base material made of a nonpolar polymer such as an olefin resin such as polyethylene and polypropylene, and a base material whose surface is coated with the release agent. Examples of the strongly adhesive substrate include a substrate made of a highly polar polymer such as polyester, and a substrate whose surface has been subjected to an oxidation treatment or the like by the above-described chemical or physical method.

  The low-adhesive substrate is used as a substrate for a substrate-peelable pressure-sensitive adhesive sheet from which a substrate and a layer on the substrate can be easily peeled off. The substrate-peelable pressure-sensitive adhesive sheet is, for example, after being adhered to one adherend a, the substrate is peeled off to leave the heat-expandable pressure-sensitive adhesive layer on the adherend a. It can be used as a temporary fixing adhesive such as bonding the adherend b. In this case, when it is desired to release the adhered state, the adherends a and b can be easily separated by heat treatment. On the other hand, the strongly adhesive substrate is used as a substrate for a substrate-fixed type pressure-sensitive adhesive sheet in which a substrate and a layer on the substrate are strongly bonded. Such a substrate-fixed pressure-sensitive adhesive sheet can be adhered to an adherend with a predetermined adhesive force at the time of adhesion, and can be easily peeled or separated by heat treatment when it is desired to release the adhered state.

  When the heat-peelable pressure-sensitive adhesive sheet is adhered to an adherend, the rubber-like organic elastic layer 2 has a function of causing the surface of the pressure-sensitive adhesive sheet to favorably follow the surface shape of the adherend so as to increase the adhesion area. When heat-peeling the pressure-sensitive adhesive sheet from an adherend, the heat expansion of the heat-expandable layer is controlled highly (accurately), and the heat-expandable layer is preferentially and uniformly expanded in the thickness direction. With function.

  The rubber-like organic elastic layer 2 is provided with the above function, for example, natural rubber, synthetic rubber, or synthetic resin having rubber elasticity having a D-type Sure D-type hardness based on ASTM D-2240 of 50 or less, particularly 40 or less. It is preferable to form with.

  Examples of the synthetic rubber or synthetic resin having rubber elasticity include nitrile-based, diene-based, and acrylic-based synthetic rubbers; polyolefin-based and polyester-based thermoplastic elastomers; ethylene-vinyl acetate copolymer, polyurethane, and polybutadiene. And synthetic resins having rubber elasticity such as soft polyvinyl chloride. In addition, even if it is essentially a hard polymer such as polyvinyl chloride, rubber elasticity can be exhibited by combination with a compounding agent such as a plasticizer or a softener. Such a composition can also be used as a constituent material of the rubbery organic elastic layer. Further, an adhesive substance such as an adhesive constituting the heat-expandable adhesive layer 3 described later can also be preferably used as a constituent material of the rubber-like organic elastic layer 2.

  The thickness of the rubbery organic elastic layer 2 is generally 500 μm or less (for example, 1 to 500 μm), preferably 3 to 300 μm, and more preferably about 5 to 150 μm.

  The rubber-like organic elastic layer 2 is formed, for example, by applying a coating liquid containing an elastic layer forming material such as the natural rubber, synthetic rubber, or synthetic resin having rubber elasticity to the substrate 1 (coating method). A method (dry lamination method) in which a film made of an elastic layer forming material or a laminated film in which a layer made of the elastic layer forming material is previously formed on one or more thermally expandable pressure-sensitive adhesive layers 3 is bonded to the substrate 1; It can be carried out by an appropriate method such as a method of co-extruding a resin composition containing the constituent material of the material 1 and a resin composition containing the elastic layer forming material (co-extrusion method).

  Note that the rubber-like organic elastic layer 2 may be formed of an adhesive substance containing natural rubber, synthetic rubber, or a synthetic resin having rubber elasticity as a main component, or a foamed film or the like mainly containing such a component. It may be formed. Foaming is a conventional method, for example, a method using mechanical stirring, a method using a reaction product gas, a method using a foaming agent, a method for removing a soluble substance, a method using a spray, a method for forming a syntactic foam, It can be performed by a sintering method or the like. The rubbery organic elastic layer 2 may be a single layer or may be composed of two or more layers.

  The heat-expandable pressure-sensitive adhesive layer 3 includes a pressure-sensitive adhesive for imparting adhesiveness and heat-expandable microspheres (microcapsules) for imparting thermal expansivity. Therefore, after adhering the pressure-sensitive adhesive sheet to the adherend, the heat-expandable pressure-sensitive adhesive layer 3 is heated at any time to expand and / or expand the heat-expandable microspheres. The pressure-sensitive adhesive sheet can be easily peeled off by reducing the area of adhesion between the substrate 3 and the adherend. With a foaming agent that is not microencapsulated, good releasability cannot be stably exhibited.

  The pressure-sensitive adhesive is preferably one that does not restrict as much as possible the expansion and / or expansion of the heat-expandable microspheres when heated. Examples of the adhesive include a rubber-based adhesive, an acrylic-based adhesive, a vinyl alkyl ether-based adhesive, a silicone-based adhesive, a polyester-based adhesive, a polyamide-based adhesive, a urethane-based adhesive, and a styrene-diene block copolymer. Known pressure-sensitive adhesives, such as a system pressure-sensitive adhesive, and a heat-curable resin having a melting point of about 200 ° C. or less mixed with these pressure-sensitive adhesives, may be used alone or in combination of two or more. (See, for example, JP-A-56-61468, JP-A-61-174857, JP-A-63-17981, JP-A-56-13040, etc.). Adhesives include, in addition to the adhesive component (base polymer), a crosslinking agent (eg, polyisocyanate, alkyl etherified melamine compound, etc.), a tackifier (eg, rosin derivative resin, polyterpene resin, petroleum resin, oil-soluble phenol) Resin), a plasticizer, a filler, an antioxidant and the like.

Generally, as the pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive based on natural rubber or various synthetic rubbers as a base polymer; alkyl (meth) acrylate (eg, methyl ester, ethyl ester, propyl ester, isopropyl ester, butyl ester, Isobutyl ester, s-butyl ester, t-butyl ester, pentyl ester, hexyl ester, heptyl ester, octyl ester, 2-ethylhexyl ester, isooctyl ester, isodecyl ester, dodecyl ester, tridecyl ester, pentadecyl ester, hexa decyl ester, heptadecyl ester, octadecyl ester, nonadecyl ester, Accession used as monomer components one or more of C, such as _1-20 alkyl ester) such as eicosyl ester Such as acrylic adhesive is used to Le-based polymer (homopolymer or copolymer) as a base polymer.

  In addition, the acrylic polymer may be added to other monomer components copolymerizable with the alkyl (meth) acrylate as necessary for the purpose of improving cohesive strength, heat resistance, crosslinkability, and the like. A corresponding unit may be included. Examples of such monomer components include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid; maleic anhydride, icotanic anhydride Acid anhydride monomers such as; hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxyhexyl (meth) acrylate, hydroxyoctyl (meth) acrylate, (meth) Hydroxyl group-containing monomers such as hydroxydecyl acrylate, hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl methacrylate; styrenesulfonic acid, allylsulfonic acid, 2- (meth) acrylic acid Sulfonic acid group-containing monomers such as mid-2-methylpropanesulfonic acid, (meth) acrylamidopropanesulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalenesulfonic acid; (meth) acrylamide, N, N-dimethyl (N-substituted) amide monomers such as (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide; aminoethyl (meth) acrylate; ) N, N-dimethylaminoethyl acrylate, aminoalkyl (meth) acrylates such as t-butylaminoethyl (meth) acrylate; methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate (Meta) acri Acid alkoxyalkyl monomers; maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide; N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N -Octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide, and other itaconimide-based monomers; N- (meth) acryloyloxymethylene succinimide, N- (meth) aculoyl-6-oxy Succinimide monomers such as hexamethylene succinimide, N- (meth) acryloyl-8-oxyoctamethylene succinimide; vinyl acetate, vinyl propionate, N-vinyl pyrrolide , Methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N-vinylcarboxylic amides, styrene, α-methylstyrene, N-vinyl Vinyl monomers such as caprolactam; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; acrylic monomers containing an epoxy group such as glycidyl (meth) acrylate; polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, ( Glycol-based acrylic ester monomers such as methoxyethylene glycol (meth) acrylate and methoxypolypropylene glycol (meth) acrylate; Acrylic ester monomers having a heterocyclic ring such as tetrahydrofurfuryl acrylate, fluorine (meth) acrylate, silicone (meth) acrylate, a halogen atom, a silicon atom, etc .; hexanediol di (meth) acrylate, (poly) ethylene glycol di (Meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, Multifunctional monomers such as dipentaerythritol hexa (meth) acrylate, epoxy acrylate, polyester acrylate, urethane acrylate; isoprene, butadiene, iso Olefin monomers such as butylene; vinyl ether monomers such as vinyl ether; One or more of these monomer components can be used.

In addition, from the viewpoint of a balance between a moderate adhesive force before the heat treatment and a decrease in the adhesive force after the heat treatment, a more preferable pressure-sensitive adhesive has a dynamic elastic modulus of 50,000 to 10,000,000 dyn / cm at ordinary temperature to 150 ° C. ^A pressure-sensitive adhesive based on polymers in the range of ² .

  As the heat-expandable microsphere, for example, any microsphere in which a substance such as isobutane, propane, pentane or the like which is easily gasified and expanded by heating is included in an elastic shell may be used. The shell is often formed of a heat-meltable substance or a substance that breaks due to thermal expansion. Examples of the material for forming the shell include a vinylidene chloride-acrylonitrile copolymer, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, and polysulfone. The heat-expandable microspheres can be produced by a conventional method, for example, a coacervation method, an interfacial polymerization method, or the like. The heat-expandable microspheres include commercially available products such as microspheres (trade name, manufactured by Matsumoto Yushi Seiyaku Co., Ltd.).

  In order to efficiently reduce the adhesive force of the pressure-sensitive adhesive layer by heat treatment, heat-expandable microspheres having a moderate strength that does not burst until the volume expansion rate is 5 times or more, especially 7 times or more, especially 10 times or more are preferable. .

  The blending amount of the heat-expandable microspheres can be appropriately set according to the expansion ratio of the pressure-sensitive adhesive layer and the property of lowering the adhesive strength, but is generally based on 100 parts by weight of the base polymer forming the heat-expandable pressure-sensitive adhesive layer 3. For example, 1 to 150 parts by weight, preferably 10 to 130 parts by weight, and more preferably 25 to 100 parts by weight.

  The heat-expandable pressure-sensitive adhesive layer 3 is prepared, for example, by preparing a coating liquid containing a pressure-sensitive adhesive and heat-expandable microspheres by using a solvent as necessary, and applying the coating liquid on the base material 1 or the rubber-like organic elastic layer 2. Method, a method of applying the coating liquid on an appropriate separator (such as release paper) to form a heat-expandable pressure-sensitive adhesive layer, and transferring (transferring) this onto the substrate 1 or the rubber-like organic elastic layer 2. Can be formed by a conventional method. The heat-expandable pressure-sensitive adhesive layer 3 may be a single layer or multiple layers.

  An important feature of the present invention is that the center line average roughness of the surface of the heat-expandable pressure-sensitive adhesive layer before heating is 0.4 μm or less (for example, about 0.02 to 0.4 μm). The center line average roughness is preferably 0.3 μm or less (for example, about 0.02 to 0.3 μm), and more preferably 0.2 μm or less (for example, about 0.02 to 0.2 μm). The maximum roughness of the surface of the heat-expandable pressure-sensitive adhesive layer before heating is preferably 5 μm or less (for example, about 0.1 to 5 μm), more preferably 3 μm or less (for example, about 0.5 to 3 μm). is there.

  The center line average roughness and the maximum roughness of the surface of the heat-expandable pressure-sensitive adhesive layer before heating are determined by appropriately selecting the thickness of the heat-expandable pressure-sensitive adhesive layer 3 and the particle size of the heat-expandable microspheres to be added to the pressure-sensitive adhesive layer. Can be adjusted.

  The particle diameter of the heat-expandable microspheres secures a center line average roughness of 0.4 μm or less on the surface of the heat-expandable pressure-sensitive adhesive layer before heating, and further, a maximum roughness of 5 μm or less on the surface of the heat-expandable pressure-sensitive adhesive layer before heating. Therefore, it is desirable that the relationship of “thickness of the heat-expandable adhesive layer 3 ≧ particle diameter of the heat-expandable microspheres” is satisfied. When the particle diameter of the heat-expandable microspheres is larger than the thickness of the heat-expandable pressure-sensitive adhesive layer 3, the surface roughness of the heat-expandable pressure-sensitive adhesive layer 3 increases, and the effective adhesive area with the adherend decreases. When the rubbery organic elastic layer 2 is provided between the base material 1 and the heat-expandable pressure-sensitive adhesive layer 3, the particle diameter of the heat-expandable microspheres is slightly larger than the thickness of the heat-expandable pressure-sensitive adhesive layer 3. This is not the case, since an absorption effect on the rubbery organic elastic layer 2 can be expected. Adjustment of the particle diameter of the heat-expandable microspheres may be performed in the process of generating the heat-expandable microspheres, or may be performed by means such as classification after the generation.

  The thickness of the heat-expandable pressure-sensitive adhesive layer 3 is preferably 300 μm or less, particularly preferably 100 μm or less. If the thickness is too large, cohesive failure occurs at the time of peeling after the heat treatment, and the pressure-sensitive adhesive remains on the adherend, and the adherend is easily contaminated. On the other hand, when the thickness of the pressure-sensitive adhesive is too small, the degree of deformation of the heat-expandable pressure-sensitive adhesive layer 3 due to the heat treatment is small, and the adhesive force is difficult to be reduced smoothly. It needs to be smaller. From this point, the thickness of the heat-expandable pressure-sensitive adhesive layer 3 is preferably 5 μm or more, more preferably 10 μm or more, and particularly preferably 15 μm or more.

  As the separator 4, a conventional release paper or the like can be used. The separator 4 is used as a protective material for the heat-expandable pressure-sensitive adhesive layer 3 and is peeled off when the pressure-sensitive adhesive sheet is adhered to the adherend. The separator 4 does not necessarily have to be provided.

  The heat-expandable pressure-sensitive adhesive layer 3 can be formed not only on one side of the substrate 1 but also on both sides. Further, the rubbery organic elastic layer 2 may be interposed on one side or both sides of the base material 1 if necessary. Furthermore, it is also possible to provide the heat-expandable pressure-sensitive adhesive layer 3 on one surface of the substrate 1 and to provide a normal adhesive layer containing no heat-expandable microspheres on the other surface. In addition, an intermediate layer such as an undercoat layer or an adhesive layer may be provided between the base material 1 and the rubber-like organic elastic layer 2 or between the rubber-like organic elastic layer 2 and the heat-expandable pressure-sensitive adhesive layer 3.

  In the heat-peelable pressure-sensitive adhesive sheet of the present invention, since the center average roughness of the surface of the heat-expandable pressure-sensitive adhesive layer before heating is small, it is used, for example, as a temporary fixing tape at the time of cutting an electronic component, and is used to make a smaller chip. Even when the target area is small, the effective contact area with the work can be sufficiently ensured, so that it is possible to suppress the occurrence of troubles due to insufficient bonding force such as chip flying or displacement. Therefore, it is possible to prevent a decrease in productivity, yield, and the like.

  Further, in a heat-peelable pressure-sensitive adhesive sheet in which a rubber-like organic elastic layer is provided between a base material and a heat-expandable pressure-sensitive adhesive layer, when the pressure-sensitive adhesive sheet is bonded to an adherend, the elasticity of the rubber-like organic elastic layer is reduced. Thereby, the surface of the pressure-sensitive adhesive sheet satisfactorily follows the surface shape of the adherend to provide a large bonding area, thereby increasing the bonding strength and, when peeling by heating, expanding the heat-expandable layer (volume). Change) can be controlled with high precision, and can be preferentially and uniformly expanded in the thickness direction, and peeling can be further facilitated. In addition, even if the particle diameter of the heat-expandable microspheres contained in the heat-expandable pressure-sensitive adhesive layer is somewhat large, unevenness due to the particle size is absorbed by the rubber-like organic elastic layer, so that the surface roughness of the heat-expandable pressure-sensitive adhesive layer is reduced. It can be kept small.

  The heat-peelable pressure-sensitive adhesive sheet of the present invention can also be used for the purpose of permanently bonding an adherend made of an appropriate article, but after adhering the adherend for a predetermined period, after achieving the bonding purpose. Is suitably used for applications where it is required or desired to release its adhesive state. In particular, it is most suitable for the production of smaller chip components, which are likely to be difficult to adhere with the conventional heat-peelable pressure-sensitive adhesive sheet, for example, the process of making electronic components such as semiconductor wafers and chips, ceramic capacitors and oscillators into smaller chips.

  The heat treatment conditions for allowing the pressure-sensitive adhesive sheet of the present invention to be easily peeled from the adherend include a decrease in the adhesive area due to the surface condition of the adherend, the type of the heat-expandable microspheres, and the like. It can be set as appropriate depending on conditions such as heat resistance of the attached body and a heating method. The general heat treatment condition is a temperature of 100 to 250 ° C. for 1 to 90 seconds (hot plate or the like) or 5 to 15 minutes (hot air dryer or the like). Under such heating conditions, the heat-expandable microspheres of the pressure-sensitive adhesive layer usually expand and / or foam, and the pressure-sensitive adhesive layer expands and deforms, and the adhesive strength is reduced or lost. Note that the heat treatment can be performed at an appropriate stage depending on the purpose of use. In some cases, an infrared lamp or heated water can be used as the heating source.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. The particle size was measured using a laser scattering / diffraction type particle size distribution analyzer SALD-2000J (manufactured by Shimadzu Corporation).

Example 1
The heat-expandable microspheres A (Matsumoto Microsphere F-50D: manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd .: average particle diameter 13.4 μm, maximum particle diameter 63 μm) are classified using a centrifugal type air classifier, and classified heat. Expandable microspheres B (average particle diameter 12.3 μm, maximum particle diameter 42 μm) were obtained.
On the other hand, 2-ethylhexyl acrylate-ethyl methacrylate-methyl methacrylate (30 parts by weight-70 parts by weight-5 parts by weight) copolymer pressure-sensitive adhesive 100 parts by weight (polyurethane-based cross-linking agent 2 parts by weight), Prepare a toluene solution containing 30 parts by weight of the classified heat-expandable microspheres B, apply it on a 100-μm-thick polyester film so that the thickness after drying becomes 45 μm, dry and heat-peel. A mold adhesive sheet was obtained.
Next, a 120 mm × 100 mm × 0.5 mm thick ceramic sheet (before firing) was temporarily fixed to the adhesive surface of the above-mentioned heat-peelable adhesive sheet, which was mounted and fixed on a dicing ring. The chip was fully cut into 0.6 mm × 0.3 mm chips. After the cut, a heat treatment at 130 ° C. for 60 seconds was performed on a hot plate in a state of being fixedly mounted on the dicing ring.

Example 2
On a 100 μm-thick polyester film, a toluene solution containing a 2-ethylhexyl acrylate-ethyl acrylate-methyl methacrylate copolymer pressure-sensitive adhesive (1 part by weight of a polyurethane-based crosslinking agent) was dried. It was applied to a thickness of 10 μm and dried to form a rubbery organic elastic layer.
In the same manner as in Example 1, the classified heat-expandable microspheres B30 were added to 100 parts by weight of a 2-ethylhexyl acrylate-ethyl acrylate-methyl methacrylate pressure-sensitive adhesive (2 parts by weight of a polyurethane-based crosslinking agent). A toluene solution prepared by blending parts by weight was prepared, and this was coated on a separator so as to have a thickness of 35 μm after drying and dried to form an adhesive layer, and then the rubbery organic elastic layer was formed. The polyester film was bonded to the rubbery organic elastic layer side to obtain a heat-peelable pressure-sensitive adhesive sheet.
Next, a 120 mm × 100 mm × 0.5 mm thick ceramic sheet (before firing) was temporarily fixed to the adhesive surface of the above-mentioned heat-peelable adhesive sheet, which was mounted and fixed on a dicing ring. The chip was fully cut into 0.6 mm × 0.3 mm chips. After the cut, a heat treatment at 130 ° C. for 60 seconds was performed on a hot plate in a state of being fixedly mounted on the dicing ring.

Example 3
In place of the classified heat-expandable microspheres B, heat-expandable microspheres C (Matsumoto Microsphere F-301D: manufactured by Matsumoto Yushi Seiyaku Co., Ltd .: average particle diameter 11.6 μm, maximum particle diameter 42 μm) are added to the adhesive layer. The same operation as in Example 1 was performed except that the heat treatment conditions after cutting the chips were set to 100 ° C. × 60 seconds.

Comparative Example 1
In place of the classified heat-expandable microspheres B, heat-expandable microspheres A (Matsumoto Microsphere F-50D: manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd .: average particle diameter 13.4 μm, maximum particle diameter 63 μm) are added to the adhesive layer. Except having performed, the same operation as Example 1 was performed.

Comparative Example 2
In place of the classified heat-expandable microspheres B, heat-expandable microspheres A (Matsumoto Microsphere F-50D: manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd .: average particle diameter 13.4 μm, maximum particle diameter 63 μm) are added to the adhesive layer. Except having performed, the same operation as Example 2 was performed.

Evaluation Test Table 1 shows the center line average roughness and the maximum roughness of the surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples before heating, and the chip retention when cutting the chips. The center line average roughness and the maximum roughness of the surface of the adhesive layer were measured by a non-contact three-dimensional surface roughness meter manufactured by ZYGO. In each of the examples and the comparative examples, no adhesive residue was observed on the chip peeling surface after the heat peeling and recovery.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing which shows an example of the heat peelable adhesive sheet of this invention. It is an outline sectional view showing other examples of a heat peeling type pressure sensitive adhesive sheet of the present invention.

Explanation of reference numerals

1 Substrate
2 Rubbery organic elastic layer
3 Thermal expansion adhesive layer
4 separator

Claims (4)

  A heat-peelable pressure-sensitive adhesive sheet provided with a heat-expandable pressure-sensitive adhesive layer containing heat-expandable microspheres on at least one side of a substrate, wherein the heat-expandable pressure-sensitive adhesive layer surface before heating has a center line average roughness of 0.1 mm. A heat-peelable pressure-sensitive adhesive sheet having a thickness of 4 μm or less.   The heat-peelable pressure-sensitive adhesive sheet according to claim 1, wherein the surface of the heat-expandable pressure-sensitive adhesive layer before heating has a maximum roughness of 5 µm or less.   The heat-peelable pressure-sensitive adhesive sheet according to claim 1 or 2, further comprising a rubbery organic elastic layer between the substrate and the heat-expandable pressure-sensitive adhesive layer.  The heat-peelable pressure-sensitive adhesive sheet according to claim 3, wherein the rubber-like organic elastic layer is formed of a pressure-sensitive adhesive substance.

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